1. Field of the Invention
Preferred aspects of the present invention relate to expandable medical implants for maintaining support of a body lumen and methods of making such implants.
2. Description of the Related Art
An important use of stents is found in situations where parts of the vessel wall or stenotic plaque blocks or occludes blood flow in the vessel. Often, a balloon catheter is utilized in a percutaneous transluminal coronary angioplasty procedure to enlarge the occluded portion of the vessel. However, the dilation of the occlusion can cause fissuring of atherosclerotic plaque and damage to the endothelium and underlying smooth muscle cell layer, potentially leading to immediate problems from flap formation or perforations in the vessel wall, as well as long-term problems with restenosis of the dilated vessel. Implantation of stents can provide support for such problems and prevent re-closure of the vessel or provide patch repair for a perforated vessel. Further, the stent may overcome the tendency of diseased vessel walls to collapse, thereby maintaining a more normal flow of blood through the vessel.
Prior stent designs have been described by Balcon et al., “Recommendations on Stent Manufacture, Implantation and Utilization,” European Heart Journal (1997), vol. 18, pages 1536-1547, and Phillips, et al., “The Stenter's Notebook,” Physician's Press (1998), Birmingham, Mich.
An important advancement in stent design has been the development of modular sliding and locking expandable stents. See e.g., U.S. Pat. Nos. 6,033,436 and 6,224,626; the entire disclosures of which are incorporated herein in their entireties by reference thereto. These stents comprise a tubular member formed by series of slidably engaged radial modules which compose the wall of the luminal space. These stents are positioned into the appropriate location in a collapsed, small diameter state and then expanded to the diameter necessary to support the vessel. The radial modules comprise locking mechanisms that enables the stent to resist recoil once expanded, locking into its large diameter state. Sliding and locking stents have many advantages over their various predecessors, including a constant longitudinal length, reduced risk of thrombosis and restenosis, greater resistance to recoil after deployment, and greater flexibility.
Previous sliding and locking stent designs required the assembly of numerous links into a tubular form, which, depending on the material used, would require welding or bonding steps in the fabrication process. These steps can be labor and machine intensive. Also, the points of bonding or welding are generally weaker than the materials they hold. Accordingly, there remains a need for a modular slide and lock stent design and methods of manufacture in which the stent is fabricated in a closed-loop and assembled state, without the need of bonding or welding, thereby providing much higher margins of mechanical safety and reliability, while reducing the number of parts and the manufacturing step required.